The present invention relates to aerodynamics relative to ballistic objects that are designed to lower noise, improve stability, maximizing maintaining velocity, and adjusting drag characteristics by means of various structural and material aspects as well as methods related thereto. In particular, embodiments include designs and methods associated with ammunition for firearms, and more particularly to subsonic ammunitions, that are capable of lowering a noise profile of a gun while having a consistent minimized drop over a distance the projectile travels. An alternative embodiment can also address designs and methods associated with the projectile and charge combination that facilitates a maximum sub-sonic speed at a given set of temperature ranges as force applied to the projectile can vary based on propellant temperature due to factors such as ambient temperatures.
As some background, ballistics can address four phases. A first phase can be termed “internal ballistics” which can cover behavior of the projectile from a time the projectile's propellant is initiated until the projectile exits a barrel. A second phase can be termed “transitional ballistics” which can cover the projectile's behavior from a time the projectile leaves the barrel's muzzle until pressure behind the projectile equalizes. External ballistics can cover behavior of the projectile after it exits the barrel/propellant pressure equalization until immediately before impact with a target. Terminal ballistics can cover behavior of the projectile when it hits its target.
While in the transitional ballistics phase, the projectile is still being propelled forward. A maximum velocity is reached at the end of the transitional ballistic phase and the beginning of the external ballistic phase. Maximum velocity of the projectile can be a primary constraint and/or concern in determining the characteristics and profile of the projectile at subsonic speeds. Multiple physical properties influence results of each of the four ballistic phases such as, for example, mass, sectional density, and aerodynamic shape.
External ballistics can have a substantial impact when determining characteristics and profile of the projectile. A design for the external ballistic phase can be determined by modifying physical properties and structural aspects that influence a projectile. One main goal when modifying these properties can include maintaining velocity and stability of the projectile as far down range as possible.
Terminal ballistics can refer to behavior and effects of the projectile when it hits a target. In some cases, a high velocity, deeper penetration projectile with a large hole is most desired. The shape, mass, and velocity of the projectile can influence penetration, so the initial kinetic energy when a projectile arrives at the target can provide general terminal ballistic characteristics. For terminal ballistic considerations, a terminal kinetic energy of the subsonic projectile can be calculated, and different aspects of structure/material associated with subsonic attributes are balanced against terminal ballistics considerations. Additionally, penetration of the subsonic projectile and a propellant weight for subsonic ammunition can be calculated to determine if the terminal ballistics of the subsonic projectile are effective.
Exemplary designs and methods associated with this disclosure can produce designs with a consistent trajectory and consistent drop while maintaining control of a projectile as well as ensuring that the projectile stays below the speed of sound in certain ballistics phases. Some exemplary designs of subsonic ammunition can address some or all four ballistic phases: internal, transitional, external, and terminal. By creating methods and designs that address the various ballistic phases, a profile of some embodiments of the exemplary subsonic projectile can be determined which can reduce ballistic drop, balance aerodynamic effects, maintain low drag, and factor in propellant charge considerations at varying temperatures. The present disclosure includes methods to determine optimal characteristics of subsonic ammunition and presents some exemplary embodiments of such a projectile.
One problem statement for an exemplary embodiment of this disclosure or the invention can include designing a projectile that, when fired at subsonic speeds, has improved ballistic characteristic over a supersonic projectile fired at subsonic speeds. Desired performance for some embodiments of the invention can include the following: maximizing an initial velocity as the projectile leaves a barrel, minimizing a reduction of velocity as the projectile travels down range, consistent flight trajectory (e.g., minimize dispersion, maximize precision). A trade-off can be whether precision (i.e. how closely the projectile impact points are grouped together) is more important than accuracy (i.e. how close an impact point is to the aim point). This tradeoff can be determined since aim point (and therefor accuracy) could always be adjusted once the projectile trajectory has been characterized and is known by a user, but precision could not be adjusted by the user in a similar manner.
An illustrative embodiment of the present disclosure can include a subsonic ammunition cartridge assembly comprising a projectile and a casing having a base end and an open end to receive the projectile. An optimized subsonic projectile can be designed having an elliptical nose cone, a body, and boattail section. The projectile can be sized to fit within the open end of the casing and can have structural aspects, e.g., meplat, nose shape/length, body shape/length, boattail shape/length, grooves, rebated or stepped sections, tail shape/length, etc, as well as charge disposed within the casing that collectively exhibit a desired degree of stability at subsonic velocity during, e.g. an external ballistics phase, as well as addressing drop, maximizing velocity at particular stages, etc. Different materials can be used for projectile designs that provide various effects to include external and terminal ballistics phase effects. In some embodiments, desired designs should strive to produce a highest minimum pressure coefficient as possible associated with the projectile during a subsonic external ballistics phase. In some embodiments, a desired design will provide the projectile with a highest maximum subsonic velocity. Pressure coefficient can also be a function of a thickness on a projectile object (e.g., a diameter). Associated methods are also provided to include methods of designing, manufacturing, assembly, and use.
Any additional features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of the illustrative embodiment exemplifying the best mode of carrying out the invention as presently perceived.